A liquid crystal display device utilizes optical anisotropy, dielectric anisotropy or the like of liquid crystal molecules in a liquid crystal composition. A classification based on an operating mode of liquid crystal molecules include a phase change (PC) mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a bistable twisted nematic (BTN) mode, an electrically controlled birefringence (ECB) mode, an optically compensated bend (OCB) mode, an in-plane switching (IPS) mode, a fringe field switching (FFS) mode and a vertical alignment (VA) mode.
A liquid crystal display device having a mode in which a polymer is combined with the liquid crystal composition is known. Specific examples of the mode include a polymer sustained alignment (PSA) mode or a polymer stabilized (PS) mode. In the liquid crystal display device having the mode, the liquid crystal composition to which a polymerizable compound is injected into a display device. The polymerizable compound is polymerized by irradiation with ultraviolet light in a state in which voltage is applied between electrodes, thereby forming the polymer in the liquid crystal composition. The method gives the liquid crystal display device in which response time is shortened and image sticking is improved.
The method can be applied to the liquid crystal display devices having various operating modes, and such modes as PS-TN, PS-IPS, PS-FFS, PSA-VA and PSA-OCB are known. The polymerizable compound used in the device having such a mode is considered to have high capacity to align the liquid crystal molecules, but solubility in the liquid crystal composition is far from high. An attempt has been made for improving the solubility in the liquid crystal composition so far, but an improvement in the solubility tends to cause a decrease in polymerization reactivity. Therefore, desire has been expressed for development of the polymerizable compound having a suitable balance between the solubility and the polymerization reactivity.